Ambient light sensors are now in widespread use, including cameras, camcorders, scanners, electrical microscopes, and so forth. The function of the ambient light sensors is to detect and convert ambient light brightness into electrical signal. For instance, knowing the brightness information of the ambient light, the display system brightness could be adjusted accordingly to reduce the power consumption of the backlight illumination. For most of the conventional ambient light sensor solutions, the sensor spectral response is not matched with the ideal human eye photometric response. The non-ideal ambient light sensor has a much wider spectral response range and also there are multiple peaks exhibited within the entire photodiode detection range of 400 nm to 1100 nm. Please refer to FIG. 1, which shows a chart of spectral response regarding the wavelength spectrum of a conventional ambient light sensor. Generally, the human eyes are capable of sensing visible light within wavelength ranging between 400 nm and 700 nm 11. The response of the conventional ambient light sensor not only detect visible light in the range of wavelength spectrum like human eyes, but also captures infrared light with wavelength above 700 nm that human eye is unable to respond. Therefore, within the range between 700 nm and 1200 nm, two peaks 12 are produced without IR blocking according to the conventional ambient light sensor. Consequently, the inconsistency would be developed such that the human eye feels the ambient light is insufficient while, on the other hand, the conventional ambient light sensor senses sufficient ambient light. In other words, the ambient light sensor senses non-visible light that human eye is unable to response and the process for sensing non-visible light causes unnecessary backlight power consumption. For this reason, this invention provides a multi-cavity Fabry-Perot filter structure utilizing the Fabry-Perot optical interference theory in order to effectively block the range from 700 nm to 1100 nm and reduce power consumption, thereby both brightness and color image processing adjustments are provided.